The present invention relates generally to a system for controlling the damping forces of shock absorbers, comprising a piezo-actuator including a piezoelectric device made up by laminating piezoelectric elements, and more particularly to such a system having an abnormality detection function.
Various types of variable damping force type shock absorbers for use in motor vehicles, for example, have been developed heretofore with a view to allowing damping force switching control with high response. One approach involves using, for the variable damping force type shock absorber, a piezo-actuator comprising a laminated piezoelectric device made up by laminating a plurality of piezoelectric elements, as disclosed in Japanese Patent Provisional Publication No. 61-85210. Generally, when driving such a piezo-actuator to control the damping force of the shock absorber, the piezo-actuator requires a high voltage (for example, several hundreds of volts), and therefore an important aspect arising in use of such a piezo-actuator relates to the need for the drive apparatus which has high reliability on application of the high voltage thereto. Occurrence of abnormalities such as trouble of the inside parts of the drive apparatus and disconnection or short between the drive apparatus and the piezo-actuator causes difficulty in meeting the requirements to adequately control the damping force of the shock absorber.